Signaling system



July 7, 1942. R. A. REID SIGNALING SYSTEM Filed July 10, 1940 @Tw BM mp m T h TRWWM Patented July 7, 1942 SIGNALING SYSTEM Ralph A. Reid, lNahant, Mass, assignor to General Electric Company, a corporation ofNcw York Application July 10, 1940, Serial No. 344,721

2 Claims.

The present invention relatesto signaling systems and particularly to signaling systemssuch as are used at street or highway intersections for controlling tralfic.

In traffic signaling systems, it is known to provide traffic controlling signals at successive street intersections timed relatively to each other and to provide at a central. point or station a master timer or controller for keeping the intersection signals in a desired timed relationship. In such systems, the mechanism at each intersection comprises an intersection timer or controller connected with suitable stop and go signals and is operated to display the stop and go signals in a desired sequence. In such signaling systems, the arrangement is such, usually, that if the signals at any intersection get out of the desired timed relation relatively to the. other signals of the system, the intersection controller or timer which efiects the operation of the signals at such intersection is actuatedby the master controller to bring the stop and go signals which it controls back into step with the other signals of the system. One arrangement utilized for this purpose is thatof stopping the intersection controller andthen starting it up at the correct time again to put thesignals at the intersection in step with the other signals of the system.

In the operation of such systems, it may occur that when the signals at an intersection get out of step with other signals in the system, they'are so far out of step that it is necessary that the controller at such intersection be caused .toefiect correction for a major portionof a signaling cycle. Heretofore, as far as I am aware, it has been the practice to make the necessary correction to bring the signals at the intersection back into step during a single signaling. cycle. This isundesirable as it means that one signaling period of a cycle is prolonged unduly, a thing which may, especially in the caseof heavy traffic along a highway, cause considerable disturbance. For example, it might happen that a major portion or an entire go period of a trafiic signal cycle would be missed, a thing which in the case of heavy traffic might cause a considerable piling. up of traffic on the highway.

The object of the present inventionis toprovide an improved construction and arrangement in a trafiic signaling system, whereby whenthe trafiic signals at an intersection getoutof step, they are brought back into step by acertain limited amount at a time,-.the resynchronizing of the signals being spread over a number of successivesignaling cycles, if needs. be. For example, should the signals at an intersection beout of step by 25 seconds then,.according toimyinvention, instead of correcting forgthis entire. amount in a single signalingv cycle, I:v correct for-.itlover a number of successive signaling. cycles-for example, three, which: would mean correcting for: 10 seconds on eachof two successive traffic signaling cycles and r correcting for: 5 seconds in'the thirdcycle. An advantageousarrangementwhere the traflic signals control trafiic along a main thoroughfare insofar. as efiecting correction with the. least disturbance to traffic at the. intersection, is tozprolong'. the go signal. on the main thoroughfare forthe number ofasuccessive cycles required to bringthe signalsinto step..

My invention. isanimprovement over themventionvset forth and claimed. in the application Serial. No.-376,587,.filedJanuary 30, 1941",. by Marsden C. Smith applicable tosignaling systems of varioustypes. In the present instance, I have elected to. illustrate it in connection with a traffiic signalingsystem as disclosed in my U, S. Patent 2,236,298, issuedMarch 25,-1941.. It istobe understood. however, that while myinventionlis well adapted for use in suchasysteimits. use: is by, no means limited theretoas itmay. be. used in connection. with any specific typeofsignalingsystemto which it may. be" found applicable.

For a better understanding of myv invention, together with'other and further objects. thereof, reference is had to the following. description taken in connection with the accompanying drawing, and. its scope will be: pointed out in the appended claims.

In the accompanying, drawing,. the.figure.-is a diagrammatic view of a trafiic control system. embodying. my invention Referring to .thisdrawingin detail, tw'o groups of trafiic signals IULand. I:l are-indicated, each group. of signals comprising; three. signals marked G, A and R, being. respectively green, amberand red-colored light signals. The groups are positioned to faceintersectinglanes of traffic respectively and .the respective signals. are

Each conductor of the cable I2 is connectedf directly or indirectly to a stationary contact l3 of a suitable controller and receives energy through a movable contact l4 from another sta tionary contact l5. The circuit for the lights continues to a suitable source through a conductor l6, closed switch contacts l1, l8, a conductor l9 and a suitable power switch to the source indicated by a plus sign. The contacts |5 are interconnected to the common supply conductor l6 so that when a movable bridging contact l4 rests on both of its pair of stationary con tacts, it closes the circuit to the respective signal lamp in that circuit to energize it.

The respective movable contacts M are moved by cams 2| one cam being provided for each movable contact. The cams are mounted on a common shaft 22 so that they may rotate in unison and their shapes are so arranged that certain ones of the contacts remain closed and certain ones of the contacts are opened in each of several predetermined positions of the shaft, 3. complete cycle of operations being performed in each revolution of the shaft.

The shaft 22 may contain cams for operating contacts in circuits other than the signal circuits. The shaft 22 carries one cam 43 used, for example, for operating contacts in a circuit arranged to maintain the shaft 22 in synchronism with a control dial. This circuit and its function will be explained later in the specification.

The shaft 22 with its group of cams is rotated step by step by a mechanism including a ratchet wheel 23 rigidly attached to the end of the shaft 22, a pawl 24 pivotally mounted on a pawl arm 25 and in operating relation with the ratchet wheel, an armature 26 and a coil 21. The pawl arm 25 is pivoted at one end on the shaft 22 and at the other end to the armature 25. The armature and pawl arm are raised to an upper position when the coil 21 is energized and the pawl 24 then engages a new notch in the ratchet wheel. When the coil 21 becomes deenergized the armature drops to its first position and the pawl, being carried by the pivoted pawl arm, rotates the ratchet wheel 23, with the shaft 22 and the cams, to a new position. The ratchet wheel illustrated has six notches whereby siX energizations of the coil 21 and corresponding movements of the pawl will effect a complete revolution of the shaft and cams. It is evident, however, that any other desired number of notches may be used and any desired combination of the contact operations may be had in each position by suitably shaping the cams to effect the opening and closing of the circuits at these shaft positions.

The intermittent energization of the coil 21 is effected and timed by contacts actuated by a rotating dial 29 having two rows of slots near its periphery. Keys 3|, and 32 are placed in certain ones of the outer row of these slots so that at the proper instances during the rotation of the dial, they will actuate suitably positioned contacts to close the circuit to the coil 21 momentarily, each actuation effecting a movement of the shaft 22 to a succeeding position.

The dial 29 is mounted on a shaft 29 driven by a motor 34 through the motor shaft 34' and a pair of gears 35, 36. The motor is preferably a synchronous motor whose armature speed is proportional to the frequency of the alternating current supplied to its operatingfield wherebythe speed of the dial remains constant as long as the frequency of the supply current remains constant. lhe motor is provided with two opposing fields 31, 38, the first being used for normal operation and the second being energized only when it is desired to stop the motor.

The keys 3|, 32 are placed in selected ones of the row of slots near the periphery of the dial. Five keys 3| and one key 32 are used. The keys 3| actuate a contact 39 mounted on a resilient supporting arm 39'. The arm 39 is rigidly mounted at one end and is provided on the underside of its free end with a suitable block which is positioned in the path of movement of the keys 3|. As the keys rotate, they successively engage the end of the block, momentarily raise it and the contact 39 which is mounted on the arm 39 directly above the block, until the contact 39 engages the contact 49. The key 3| continues to rotate and passes beyond the block, after the two contacts have engaged, and the resilient arm returns the contact 39 to its original position thereby separating the contacts 39, 40 and breaking the circuit therethrough. The circuit closed by the engagement of the two contacts 39, 40 may be traced from the source at power switch 20, through conductor 28 to the contacts 40, 39 through the resilient arm 39 to a conductor 40', to stationary contacts 4| 42, through a movable contact 43, conductors 44, 45, switch 46 to coil 21 and to ground. There are five keys 3| in the dial 29 which provide for five energizations of the coil 21 during a single rotation of the dial 29. It is desirable, however, to have the dial 29 make one complete revolution for each complete revolution of the shaft 22 and cams 2|, and it is further desirable to maintain a synchronous relationship between these two rotating bodies so that the dial may thereby become an indicator for the position of the cam shaft and the relative spacings between keys will be a criterion for the desired period lengths of a cycle. For effecting a sixth energization of the coil 21 in each revolution of the dial, the key 32 is provided. The key 32 is provided with a notch 32 so that this key will not actuate the contact 39. It will, however, actuate a second contact 41 to close a circuit to the coil 21. This contact 41 is mounted on a contact arm 41' which isin turn connected to the coil 21 through conductors 50, 45 and switch 46. The key 32 raises contact 41 into engagement with a stationary contact 49 which is connected to the current source at the power switch 20 through conductor 54, contacts l1, l8, conductor l9 and power switch 20. Only one key 32 is used in the dial and there is, therefore, only one position of the dial at which this operation takes place. At the corresponding position of the cam shaft, the keys 3| are made ineffective to advance the cam shaft. The cam 43' on the shaft 22, provided for this purpose, opens the circuit through contacts 4|, 42 at this position by lifting the movable contact 43. The normal circuit, through which the keys 3| advance the cam shaft, is thereby opened and the cam shaft 22 remains stationary until the key 32 is advanced by the dial to close the contacts 41, 48. In this way, the cam shaft is advanced by keys 3| until it reaches this position at which the cam 43 opens this circuit. It then remains stationary until the dial moves key 32 into position to actuate the contacts 41, 48. The dial and cam shaft are then in the proper operating relationship. This relationship exists during normal operation and involves no unnecessary delay in the advance of the cam shaft because key 32 being placed in a desired slot between two keys 3| functions exactly as a key 3| to advance the camshaft to its next position at the proper instant. of the. operating cycle.

It is at. times desirable to advance the cam shaft by a. hand-operated .switch independently of the. dial. If such operation is desired, the.

switch. t isv moved from its illustrated. position.

to. a second position inwhich it connects the coil 21 to a. conductor. 55.. This conductor may be connected to. the common current supply source by ahand-operated switch 56 and a conductor 51. When. switch fliiis in. this second position, therefore, themere actuation of the switch 56 will advance the cam shaft 22.

It is alsodesirable at times to operate thesignals simply to: indicate caution. For this purpose, the switch 59. is provided having control of thecontacts l1, id through which the current normally flows to the signals. Whenthese contactsare separated,.the common circuit to all the. signalsis interrupted and. the normal sequential operation of the signals ceases. The switch 59 is further provided with movable contacts 5!, 62. These. contacts are. respectively connected to the caution signals through conductors. 83, t5 and for normal. operation are in position to engage contacts 65, 66 connected to contacts i3 on the cam. switch. for sequential operation by cams on the shaft 22. For operating the caution signals alone, the switch 59. may be moved to a second position, thereby to move the. contact 5! into engagement with a contact iii-3 and to move the contacto2 into engagement with a contact it.

Contacts 69, 10. are connected by a conductor TI to acontact arm i3 pivotally mounted on a stationary block iii and operable intermittently to open and close a pair of contacts l5, 15. A star wheel Ml mounted on the motor shaft 35 actuates the contact arm 13. The contact '55 is connected to the common current source through a conductor ll, conductor l9. and power switch 20. When switch59 is therefore moved to its second position,,the signals of both groups iii and H are deenergizedby the separation of contacts H, H! andonly theamber or caution signals are energized. through. the newly closed contacts 85, 69 and 62, iii and through the flashing device just described. When switch 59 is moved to its second position the contacts H, l8 being separated, thekey 32, uponactuation of thev contact 41, cannot establish the circuit to the coil 21. The keys 31, however, will continue to close the circuit to coil 2]. until the cam shaft reaches the position at. which this circuit is opened by contact 43.

In accordance with my invention, the controller above described may be brought into synchronism with a master controller and with other similar controllers within a system by delaying the movement of the controller for small periods during several successive cycles of operation if the time required toplace it into synchronism exceeds a predetermined value. The master controller 19 used in this system is provided with a rotating cam Bil which rotates at the speed at which the secondary dials are intended to operate and is caused momentarily to actuate a switch 8| once during each revolution. The switch BI is connected between a current source and a common conductor 82. When the switch 8| is closed, current is fed to the respective controllers through conductor 82 and branch conductors 83, 83a, 831), etc. Branch conductors 83a, 83?); etc., lead to controllers at other intersections which controllers are in parallel with the one illustrated in detail and operate in a similar manner. Conductor 83 in the described controller is connected to a by enabling it to resilient contact arm 84 having acontact t5 operable by a key. 33" placedin the second'row of slots in the dial 29. The arm Sflis placed next to the arm '51 and thekey' 33 is made longer than either key 3! or 32 so that itmay engage the extended block on the underside of the contact arm. At a predetermined,positionof the dial, the contact 85 is raised. into engagement with a contact 85 and a circuit is established to the braking field 38 on the motor 35 through a conductor 88, a switch 89 and a conductor 99. Only one key 33 is used so that one actuation of the contact 85 is obtained at each revolution of the dial 29. If at the instant at which the contact 85 engages the contact 36 the master controller switch BI is closed and current is fed to the braking field 38, the motor stops until such cam .83 opens the switch 8i. At that instant, the braking coil 38 becomes deenergized. The key 33 moves beyond the actuating block of the contact t5 and'the circuit is opened.

As previously stated, it is possible for the secondary controller to be out of step with the master timer by a period equalling the greater portion of an operating cycle. To bring the controller into synchronism, it would be necessary in the systems heretofore used,'to hold it stationary for this comparatively long period of time and that would result in an undesirable delay of traffic. A time, limiting switch is, therefore, provided in the braking coil circuit to release the timer after a predetermined" short period of time, thereoperate for one complete cycle before it is again stopped due to its being out of synchronism. The timer is stopped through successive cycles, for this period of time as determined by the time limiting switch, until the timer is brought into synchronism. In the latter case, the braking coil circuit is opened by the master timer at the instant at which synchronism is reached and the time limiting switch merely returns to normal condition ready for an operation at a subsequent period. To carry out this operation, any suitable time delay switch may be used. In the present case, a simple thermostatic switch is illustrated. When current flows to the braking field 3&3, it flows through the switch 89, which preferably comprises a stationary contact and a cooperating bimetallic element. Current also flows through a heater 9i placed in operating relationship with the switch 89 and is connected between the conductor 88 and ground. Current flows through this heater only when the master controller switch 8i and the contacts 85, 86 are closed. If current flows through the heater 9| for a predetermined time, the switch 85 breaks the circuit between conductors 88 and 93, thereby deenergizes the field 38 and permits the mote-r 33 to rotate the dial sufiiciently to break the circuit at the contacts 85, 8B. The dial will, therefore, rotate for another complete revolution, still out of synchronism with the other controllers but by a smaller amount, until its key 33 again closes the circuit through contacts 85, 85. If the master switch 8! is then opened within the period set for the switch 89, there will be no operation of the thermostatic switch 89, the dial will continue operation in synchronism with the master timer and the heater 9| will cool off to normal temperature.

In operation of the above system, each trafiic signal controller is set into motion by energizing the motor field 31. A, switch 92 is provided, for this purpose, which closes a circuit from the time as the master.

common source at switch 20 through conductor 48, conductor 93, switch 92 and conductor 94. A closure of the switch 28 then provides current for the signaling circuits and a movement of switch 46, to the position shown, prepares the controller for automatic operation. The motor then drives the dial and the keys 3| actuate the contact 39 thereby effecting a rotation of the shaft 22 up to the position at which cam 43 opens the circuit established by the keys 3| and contact 39. The drum will then remain stationary until the dial moves to the position at which the key 32 actuates the contact 47. The shaft 22 and the dial 29 are then in synchronism with each other. During this operation the key 33 also moves with the dial and in each revolution of the dial it closes the circuit to the braking field 38 by the closure of contacts 85, 86. If the dial is in synchronism with the master timer, the switch 8| will be opened at that same instant and nothing happens. If the dial is out of synchronism with the master, the dial will be stopped or at least slowed down until it is released either by the opening of the master controller switch 8| or by the opening of the switch 89.

If the time period required to place this dial in synchronism with the master timer is greater than the time limit for which the switch 89 is set, the switch 89 will open the circuit to the braking coil 38, the dial will begin to move and will open the braking coil circuit at the contacts 85, 86. The dial will then continue for a complete revolution during which the switch 89 cools oil and returns to normal closed position. At the next actuation of the contacts 85, 8B, the braking coil will again be energized and. the thermostatic switch 89 will again be heated by current in the resistor 9|. If the dial 29 comes into synchronous relationship with the master timer before the switch 89 operates, the master switch 8| will be opened, the braking coil 38 will be deenergized and the dial 29 will again begin to rotate. The key 33 again opens the braking coil circuit at contacts 85, 86 so that upon a reclosure of the master switch 8|, the braking coil 38 remains deenergized. The number of cycles over which this operation is distributed is dependent upon the time for which the thermostatic switch is set and upon the period by which the controller is out of step with the master controller. A period of ten seconds has been found satisfactory in one installation but any other period may be used, dependent upon the trafiic conditions existing at an intersection.

The position of the key 33 in the dial is determined by the progression timing of the controller relative to the other controllers in the system. Because of this timing requirement it may happen that the dial is held up during a signal period other than the main street green period. It has been found in practice however that in practically all cases there is better than an even chance that the resynchronizing key 33 will be in the main street green period. The short delay periods distributed over several cycles become practically unnoticed when they fall into the main street green period and cause little disturbance in trafiic flow when they fall in signal periods other than the main street green period.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a traific signal system, the combination of a master controller, a secondary controller, means for continuously operating said secondary controller through a predetermined cycle of operations, braking means in said secondary controller, means operated by said secondary controller at predetermined positions during its operation to energize said braking means, means operated by said master controller for deenergizing said braking means at one instant in each cycle of operations of the secondary controller, and a thermostatic switch in the circuit of said braking means in said secondary controller operable to deenergize said braking means Within a predetermined time period after the operation of said brake-energizing means in said secondary controller thereby superceding the operation of said master controller if the time period of the thermostatic switch expires before the instant of operation of said master switch in any one cycle of operations.

2. In a trafiic signal control system, the combination of a master controller, a series of secondary controllers, braking means in each of said secondary controllers, means for energizing said braking means at a predetermined position of said secondary controllers respectively, a common conductor normally energized and connected to said secondary controllers to conduct current to said braking means respectively, means in said master controller for momentarily deenergizing said common conductor once during each cycle of operation thereby efiecting a resumption of operation of said secondary controllers simultaneously, and a thermostatic switch in each of said secondary controllers operable to deenergize the braking means in said secondary controllers respectively after a predetermined time period after its energization to limit the time delay in any one cycle of each controller respectively.

RALPH A. REID. 

